11.3: DNA Replication

Pre-Class Review: DNA stands for: –Deoxyribonucleic Acid DNA is an example of a polymer called: –Nucleic Acid Nucleic Acids are made up of: –Nucleotides; which have 3 parts to them: 1. Sugar (deoxyribose) 2. Phosphate group 3. Nitrogenous Base

Pre-Class Review: CROSS OUT 2 Categories of Bases: –Pyrimidines How many rings? –1–1 Examples: –Cytosine, (Uracil), Thymine = CUT –Purines How many rings? –2–2 Examples: –Adenine, Guanine

DNA Replication Before a cell divides, forming new cells, a complete set of genetic instructions is generated for each new cell. When an organism reproduces, genetic instructions pass from 1 generation to the next. For this to occur, there must be a means of copying the instructions. Where does this occur? –Nucleus

DNA Replication is a Semi-conservative process Each NEW set of DNA has 1 old strand and 1 new strand from new nucleotides brought in. The “ template mechanism ” uses part of the original strand as a template to be used to create a new strand. This ensures that each new cell receives an exact copy of all the genetic material and instructions.

DNA Replication Details… 1. The DNA unzipping enzyme, DNA Helicase, binds to the DNA strand and begins to uncoil/unzip the double stranded DNA strand at the hydrogen bonds. 2. As the strand separates, a “ replication bubble ” forms. This is the actual site where replication occurs.

DNA Replication Details… 3. Another enzyme, DNA polymerase, brings in new complementary DNA nucleotides into the replication bubble. 4. Complementary pairs are formed between the old strand (template) and the new DNA nucleotides (forming the new strand).

DNA Replication Details… 5. DNA POLYMERASE proofreads the newly formed DNA strands. (you don ’ t want mistakes which can lead to mutations!) 6. The replication bubble will move/travel down the entire length of the DNA strand.

DNA Replication Details… 7. Once the entire length of DNA has been copied, the replication bubble will close up. 8. DNA will recoil and begin to function. 9. How many sets of DNA? 2 total: both exact to each other! 10. The cell is ready for cell division.

DRAWING